This is a National Stage Application under 35 U.S.C. 371, based on International Application No. PCT/EP 95/02,493, filed Jun. 27, 1995.
1. Field of the Invention
The present invention relates to biodegradable polyesteramides P1 obtainable by reacting a mixture consisting essentially of
(a1) a mixture consisting essentially of
35-95 mol % of adipic acid or ester-forming derivatives thereof or mixtures thereof,
5-65 mol % of terephthalic acid or ester-forming derivatives thereof or mixtures thereof, and
0-5 mol % of a compound containing sulfonate groups,
where the total of the individual mole percentages is 100 mol %, and
(a2) a mixture consisting essentially of
(a21) 99.5-0.5 mol % of a dihydroxy compound selected from the group consisting of C2-C6-alkanediols and C5-C10-cycloalkanediols,
(a22) 0.5-99.5 mol % of an amino-C2-C12-alkanol or an amino-C5-C10-cycloalkanol, and
(a23) 15 50 mol % of a diamino-C1-C8-alkane,
(a24) 0-50 mol % of a 2,2xe2x80x2-bisoxazoline of the general formula 
where R1 is a single bond, a (CH2)q alkylene group with q=2, 3 or 4, or a phenylene group, where the total of the individual mole percentages is 100 mol %, and where the molar ratio of (a1) to (a2) is chosen in the range from 0.4:1 to 1.5:1,
with the proviso that the polyesteramides P1 have a molecular weight (Mn) in the range from 4000 to 40,000 g/mol, a viscosity number in the range from 30 to 350 g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polyesteramide P1 at 25xc2x0 C.) and a melting point in the range from 50 to 220xc2x0 C., and with the further proviso that from 0 to 5 mol %, based on the molar amount of component (a1) used, of a compound D with at least three groups capable of ester formation are used to prepare the polyesteramides P1.
The invention furthermore relates to polymers and biodegradable thermoplastic molding compositions as claimed in the dependent claims, processes for the preparation thereof, the use thereof for producing biodegradable moldings, and adhesives, biodegradable moldings, foams and blends with starch obtainable from the polymers and molding compositions according to the invention.
2. Description of the Related Art
Polymers which are biodegradable, ie. decompose under environmental influences in an appropriate and demonstrable time span have been known for some time. This degradation usually takes place by hydrolysis and/or oxidation, but predominantly by the action of microorganisms such as bacteria, yeasts, fungi and algae. Y. Tokiwa and T. Suzuki (Nature, 270 (1977) 76-78) describe the enzymatic degradation of aliphatic polyesters, for example including polyesters based on succinic acid and aliphatic diols.
EP-A 565,235 describes aliphatic copolyesters containing [xe2x80x94NHxe2x80x94C(O)Oxe2x80x94] groups (urethane units). The copolyesters of EP-A 565,235 are obtained by reacting a prepolyester, which is obtained by reacting essentially succinic acid and an aliphatic diol, with a diisocyanate, preferably hexamethylene diisocyanate. The reaction with the diisocyanate is necessary according to EP-A 565,235 because the polycondensation alone results only in polymers with molecular weights such that they display unsatisfactory mechanical properties. A crucial disadvantage is the use of succinic acid or ester derivatives thereof to prepare the copolyesters because succinic acid and derivatives thereof are costly and are not available in adequate quantity on the market. In addition, the polyesters prepared using succinic acid as the only acid component are degraded only extremely slowly.
WO 92/13019 discloses copolyesters based predominantly on aromatic dicarboxylic acids and aliphatic diols, where at least 85 mol % of the polyesteramide diol residue comprise a terephthalic acid residue. The hydrophilicity of the copolyester is increased and the crystallinity is reduced by modifications such as the incorporation of up to 2.5 mol % of metal salts of 5-sulfoisophthalic acid or short-chain ether diol segments such as diethylene glycol. This is said in WO 92/13019 to make the copolyesters biodegradable. However, a disadvantage of these copolyesters is that the biodegradation by microorganisms was not demonstrated, on the contrary only the behavior towards hydrolysis in boiling water or, in some cases, also with water at 60xc2x0 C.
According to the statements of Y. Tokiwa and T. Suzuki (Nature, 270 (1977) 76-78 or J. of Appl. Polymer Science, 26 (1981) 441-448), it may be assumed that polyesters which are essentially composed of aromatic dicarboxylic acid units and aliphatic diols, such as PET (polyethylene terephthalate) and PBT (polybutylene terephthalate), are not enzymatically degradable. This also applies to copolyesters which contain blocks composed of aromatic dicarboxylic acid units and aliphatic diols.
Furthermore, Y. Tokiwa, T. Suzuki and T. Ando (J. of Appl. Polym. Sci. 24 (1979) 1701-1711) prepared polyesteramides and blends of poly-caprolactone and various aliphatic polyamides such as polyamide-6, polyamide-66, polyamide-11, polyamide-12 and polyamide-69 by melt condensation and investigated their biodegradability by lipases. It was found that the biodegradability of such polyesteramides depends greatly on whether there is a predominantly random distribution of the amide segments or, for example, a block structure. In general, amide segments tend to reduce the rate of biodegradation by lipases.
However, the crucial factor is that no lengthy amide blocks are present, because it is known from Plant. Cell Physiol. 7 (1966) 93, J. Biochem. 59 (1966) 537 and Agric. Biol. Chem. 39 (1975) 1219 that the usual aliphatic and aromatic polyamides are biodegradable at the most only when oligomers, otherwise not.
Witt et al. (handout for a poster at the International Workshop of the Royal Institute of Technology, Stockholm, Sweden, Apr. 21-23, 1994) describe biodegradable copolyesters based on 1,3-propanediol, terephthalic ester and adipic or sebacic acid. A disadvantage of these copolyesters is that moldings produced therefrom, especially sheets, have inadequate mechanical properties.
It is an object of the present invention to provide polymers which are degradable biologically, ie. by microorganisms, and which do not have these disadvantages. The intention was, in particular, that the polymers according to the invention be preparable from known and low-cost monomer units and be insoluble in water. It was furthermore the intention that it be possible to obtain products tailored for the desired uses according to the invention by specific modifications such as chain extension, incorporation of hydrophilic groups and groups having a branching action. The aim was moreover that the biodegradation by microorganisms should not be achieved at the expense of the mechanical properties in order not to restrict the number of applications.
We have found that this object is achieved by the polymers and thermoplastic molding compositions defined at the outset.
We have furthermore found processes for the preparation thereof, the use thereof for producing biodegradable moldings and adhesives, and biodegradable moldings, foams, blends with starch and adhesives obtainable from the polymers and molding compositions according to the invention.
The polyesteramides P1 according to the invention have a molecular weight (Mn) in the range from 4000 to 40,000, preferably from 5000 to 35,000, particularly preferably from 6000 to 30,000, g/mol, a viscosity number in the range from 30 to 350, preferably from 50 to 300, g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polyesteramide P1 at 25xc2x0 C.) and a melting point in the range from 50 to 220, preferably from 60 to 220xc2x0 C.
The polyesteramides P1 are obtained according to the invention by reacting a mixture consisting essentially of
(a1) a mixture consisting essentially of
35-95, preferably from 45 to 80, mol % of adipic acid or ester-forming derivatives thereof, in particular the di-C1-C6-alkyl esters such as dimethyl, diethyl, dipropyl, dibutyl, dipentyl and dihexyl adipate, or mixtures thereof, preferably adipic acid and dimethyl adipate, or mixtures thereof,
5-65, preferably 20-55, mol % of terephthalic acid or ester forming derivatives thereof, in particular the di-C1-C6-alkyl esters such as dimethyl, diethyl, dipropyl, dibutyl, dipentyl or dihexyl terephthalate, or mixtures thereof, preferably terephthalic acid and dimethyl terephthalate, or mixtures thereof, and
0-5, preferably from 0 to 3, particularly preferably from 0.1 to 2, mol % of a compound containing sulfonate groups,
where the total of the individual mole percentages is 100 mol %, and
(a2) a mixture consisting essentially of
(a21) 99.5-0.5, preferably 99.5-50, particularly preferably 98.0-70, mol % of a dihydroxy compound selected from the group consisting of C2-C6-alkanediols and C5-C10-cycloalkanediols,
(a22) 0.5-99.5, preferably 0.5-50, particularly preferably 1-30, mol % of an amino-C2-C12-alkanol or of an amino-C5-C10-cycloalkanol, and
(a23) 0-50, preferably from 0 to 35, particularly preferably from 0.5 to 30, mol % of a diamino-C1-C8-alkane,
(a24) 0-50, preferably 0-30, particularly preferably 0.5-20, mol % of a 2,2xe2x80x2-bisoxazoline of the general formula I. 
where R1 is a single bond, an ethylene, n-propylene or n-butylene group, or a phenylene group, and R1 is particularly preferably n-butylene, where the total of the individual mole percentages is 100 mol %,
where the molar ratio of (a1) to (a2) is chosen in the range from 0.4:1 to 1.5:1, preferably from 0.6:1 to 1.1:1.
The compound containing sulfonate groups which is normally employed is an alkali metal or an alkaline earth metal salt of a dicarboxylic acid containing sulfonate groups, or the ester-forming derivatives thereof, preferably alkali metal salts of 5-sulfoisophthalic acid or mixtures thereof, particularly preferably the sodium salt.
The dihydroxy compounds (a21) employed according to the invention are selected from the group consisting of C2-C6-alkanediols, C5-C10-cycloalkanediols, the latter also including 1,2-cyclohexanedimethanol and 1,4-cyclohexanedimethanol, such as ethylene glycol, 1,2- and 1,3-propanediol, 1,2- and 1,4-butanediol, 1,5-pentanediol or 1,6-hexanediol, in particular ethylene glycol, 1,3-propanediol and 1,4-butanediol, cyclopentanediol, 1,4-cyclohexanediol and mixtures thereof.
The amino-C2-C2-alkanol or amino-C5-C10-cycloalkanol (component (a22)), this being intended also to include 4-aminomethylcyclohexanemethanol, which is preferably employed is an amino-C2-C6-alkanol such as 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, 5-aminopentanol, 6-aminohexanol and amino-C5-C6-cycloalkanols such as aminocyclopentanol and aminocyclohexanol, or mixtures thereof.
The diamino-C1-C8-alkane which is preferably employed is a diamino-C4-C6-alkane such as 1,4-diaminobutane, 1,5-diaminopentane and 1,6-diaminohexane (hexamethylenediamine, HMD).
The compounds of the general formula I (component a24) are, as a rule, obtainable by the process of Angew. Chem. int. Edit. 11 (1972) 287-288.
From 0 to 5, preferably from 0.01 to 4 mol %, based on component (a1), of at least one compound D with at least three groups capable of ester formation are used according to the invention.
The compounds D preferably contain three to ten functional groups capable of forming ester linkages. Particularly preferred compounds D have three to six functional groups of this type in the molecule, in particular three to six hydroxyl groups and/or carboxyl groups. Examples which may be mentioned are:
tartaric acid, citric acid, malic acid;
trimethylolpropane, trimethylolethane;
pentaerythritol;
polyethertriols;
glycerol;
trimesic acid;
trimellitic acid or anhydride;
pyromellitic acid or dianhydride and
hydroxyisophthalic acid.
When compounds D which have a boiling point below 200xc2x0 C. are used in the preparation of the polyester amides P1 , a proportion may distil out of the polycondensation mixture before the reaction.
It is therefore preferred to add these compounds in an early stage of the process, such as the transesterification or esterification stage, in order to avoid this complication and in order to achieve the maximum possible uniformity of their distribution within the polycondensate.
In the case of compounds D which boil above 200xc2x0 C., they can also be employed in a later stage of the process. By adding the compound D it is possible, for example, to alter the melt viscosity in a desired manner, to increase the impact strength and to reduce the crystallinity of the polymers or molding compositions according to the invention.
The preparation of the biodegradable polyesteramides P1 is known in principle (Sorensen and Campbell, Preparative Methods of Polymer Chemistry, Interscience Publishers, Inc., New York, 1961, pages 111-127; Kunststoff-Handbuch, Volume 3/1, Carl Hanser Verlag, Munich, 1992, pages 15-23) (preparation of polyesteramides); WO 92/13019; EP-A 568,593; EP-A 565,235; EP-A 28,687 (preparation of polyesters); Encycl. of Polym. Science and Eng. Vol. 12, 2nd ed., John Wiley and Sons, 1988,pages 1-75, in particular pages 59 and 60; GB 818,157; GB 1,010,916; GB 1,115,512), so that details on this are superfluous.
Thus, for example, the reaction of dimethyl esters of component a1 with component a2 can be carried out at from 160 to 230xc2x0 C. in the melt under atmospheric pressure, advantageously under an inert gas atmosphere.
In a preferred embodiment, first the required amino hydroxy compound (a22) is reacted with component (a1), preferably terephthalic acid, dimethyl terephthalate, adipic acid, di-C2-C6-alkyl adipate, succinic anhydride, phthalic anhydride, in a molar ratio of 2:1.
In another preferred embodiment, the required diamine compound (a23) is reacted with component (a1), preferably terephthalic acid, dimethyl terephthalate, adipic acid, di-C2-C6-alkyl adipate, succinic anhydride, phthalic anhydride, in a molar ratio of at least 0.5:1, preferably 0.5:1.
In another preferred embodiment, the required bisoxazoline (a24) is reacted with component (a1), preferably terephthalic acid, dimethyl terephthalate, acipic acid, di-C2-C4-alkyl adipate, succinic anhydride, phthalic anhydride, in a molar ratio of at least 0.5:1, preferably 0.5:1.
In the case of a mixture of at least one amino hydroxy compound (a22) and at least one diamino compound (a23) and at least one 2,2xe2x80x2-bisoxazoline (a24), these are expediently reacted with component (a1) in the molar amounts stated in the abovementioned preferred embodiments.
In the preparation of the biodegradable polyesteramide P1, it is advantageous to use a molar excess of component (a2) relative to component (a1), for example up to 2xc2xd times, preferably up to 1.67 times.
The biodegradable polyesteramide P1 is normally prepared with the addition of suitable conventional catalysts (Encycl. of Polym. Science and Eng., Vol. 12, 2nd ed., John Wiley and Sons, 1988, pages 1-75, in particular pages 59 and 60; GB 818,157;GB 1,010,916; GB 1,115,512), for example metal compounds based on the following elements such as Ti, Ge, Zn, Fe, Mn, Co, Zr, V, Ir, La, Ce, Li and Ca, preferably organometallic compounds based on these metals, such as salts of organic acids, alkoxides, acetyacetonates and the like, particularly preferably based on lithium, zinc, tin and titanium.
When dicarboxylic acids or anhydrides thereof are used as component (a1), esterification thereof with component (a2) can take place before, at the same time as or after the transesterification. In a preferred embodiment, the process described in DE-A 23 26 026 for preparing modified polyalkylene terephthalates is used.
After the reaction of components (a1) and (a2), the polycondensation is carried out as far as the desired molecular weight, as a rule under reduced pressure or in a stream of inert gas, for example of nitrogen, with further heating to from 180 to 260xc2x0 C.
In order to prevent unwanted degradation and/or side reactions, it is also possible in this stage of the process if required to add stabilizers. Examples of such stabilizers are the phosphorus compounds described in EP-A 13 461, U.S. Pat. No. 4,328,049 or in B. Fortunato et al., Polymer Vol. 35, No. 18, pages 4006-4010, 1994, Butterworth-Heinemann Ltd. These may also in some cases act as inactivators of the catalysts described above. Examples which may be mentioned are: organophosphites, phosphonous acid and phosphorous acid, and the alkali metal salts of these acids. Examples of compounds which act only as stabilizers are: trialkyl phosphites, triphenyl phosphite, trialkyl phosphates, triphenyl phosphate and tocopherol (vitamin E) (obtainable as UvinulR 2003A0 (BASF) for example).
On use of the biodegradable copolymers according to the invention, for example in the packaging sector, eg. for foodstuffs, it is as a rule desirable to select the lowest possible content of catalyst employed and not to employ any toxic compounds. In contrast to other heavy metals such as lead, tin, antimony, cadmium, chromium, etc., titanium and zing compounds are nontoxic as a rule (Sax Toxic Substance Data Book, Shizuo Fujiyama, Maruzen, K. K., 360 S. (cited in EP-A 565,235), see also Rxc3x6mpp Chemie Lexikon Vol. 6, Thieme Verlag, Stuttgart, New York, 9th Edition, 1992, pages 4626-4633 and 5136-5143). Examples which may be mentioned are: dibutoxydiacetoacetoxytitanium, tetrabutyl orthotitanate and zinc(II) acetate.
The ratio by weight of catalyst to polyesteramide P1 is normally in the range from 0.01:100 to 3:100, preferably from 0.05:100 to 2:100, it also being possible to employ smaller amounts, such as 0.0001:100, in the case of highly active titanium compounds.
The catalyst can be employed right at the start of the reaction, directly shortly before the removal of the excess diol or, if required, also distributed in a plurality of portions during the preparation of the biodegradable polyesteramides P1. It is also possible if required to employ different catalysts or mixtures thereof.
The biodegradable polyesteramides P2 according to the invention have a molecular weight (Mn) in the range from 4000 to 40,000, preferably from 5000 to 35,000, particularly preferably from 8000 to 35,000, g/mol, a viscosity number in the range from 30 to 450, preferably from 50 to 400, g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polyesteramide P2 at 25xc2x0 C. ) and a melting point in the range from 50 to 255, preferably from 60 to 255xc2x0 C.
The biodegradable polyesteramides P2 are obtained according to the invention by reacting a mixture consisting essentially of
(b1)a mixture consisting essentially of
35-95, preferably from 45 to 80, particularly preferably from 45 to 70, mol % of adipic acid or ester-forming derivatives thereof or mixtures thereof,
5-65, preferably from 20 to 55, particularly preferably from 30 to 55, mol % of terephthalic acid or ester-forming derivatives thereof or mixtures thereof, and
0-5, preferably from 0 to 3, particularly preferably from 0.1 to 2, mol % of a compound containing sulfonate groups,
where the total of the individual mole percentages is 100 mol %,
(b2) mixture (a2),
where the molar ratio of (b1) to (b2) is chosen in the range from 0.4:1 to 1.5:1, preferably from 0.6:1 to 1.1:1,
(b3)from 0.01 to 40, preferably from 0.1 to 30, particularly preferably from 0.5 to 20%, by weight, based on component (b1), of an amino carboxylic acid B1, and
(b4)from 0 to 5, preferably from 0 to 4, particularly preferably from 0.01 to 3.5, mol %, based on component (b1), of compound D,
where the amino carboxylic acid B1 is selected from the group consisting of the natural amino acids, polyamides with a molecular weight not exceeding 18,000 g/mol, preferably not exceeding 15,000 g/mol, and compounds which are defined by the formulae IIa or IIb 
where p is an integer from 1 to 1500, preferably from 1 to 1000, r is 1, 2, 3 or 4, preferably 1 and 2, and G is a radical selected from the group consisting of phenylene, xe2x80x94(CH2)nxe2x80x94, where n is an integer from 1 to 12, preferably 1, 5 or 12, xe2x80x94C(R2)Hxe2x80x94 and xe2x80x94C(R2)HCH2 where R2 is methyl or ethyl, and polyoxazolines of the general formula III 
where R3 is hydrogen, C1-C6-alkyl, C5-C8-cycloalkyl, phenyl which is unsubstituted or substituted up to three times by C1-C4-alkyl groups, or tetrahydrofuryl.
The natural amino acids which are preferably used are the following: glycine, aspartic acid, glutamic acid, alanine, valine, leucine, isoleucine, tryptophan, phenylalanine and oligo- and polymers obtainable therefrom, such as polyaspartimides and polyglutamimides, particularly preferably glycine.
The polyamides employed are those obtainable by polycondensation of a dicarboxylic acid with 4 to 6 carbon atoms and a diamine with 4 to 10 carbon atoms, such as tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine and decamethylenediamine.
Preferred polyamides are polyamide-46, polyamide-66 and polyamide-610. These polyamides are generally prepared by conventional methods. It is self-evident that these polyamides can contain conventional additives and auxiliaries and that these polyamides can be prepared by using appropriate regulators.
The polyoxazolines III are, as a rule, prepared by the process described in DE-A 1,206,585.
Particularly preferred compounds defined by the formulae IIa or IIb are: 6-aminohexanoic acid, caprolactam, laurolactam and the oligomers and polymers thereof with a molecular weight not exceeding 18,000 g/mol.
The biodegradable polyesteramides P2 are expediently prepared in a similar way to the preparation of the polyesteramides P1, it being possible to add the amino carboxylic acid B1 both at the start of the reaction and after the esterification or transesterification stage.
The biodegradable polyesteramides Q1 according to the invention have a molecular weight (Mn) in the range from 5000 to 50,000, preferably from 6000 to 40,000, particularly preferably from 8000 to 35,000, g/mol, a viscosity number in the range from 30 to 450, preferably from 50 to 400, g/ml (measured in o-dichlorobenzene/ phenol) (50/50% by weight) at a concentration of 0.5% by weight of polyesteramide Q1 at 25xc2x0 C.) and a melting point in the range from 50 to 255, preferably from 60 to 255xc2x0 C.
The polyesteramides Q1 are obtained according to the invention by reacting a mixture consisting essentially of
(c1) polyesteramide P1,
(c2) 0.01-50, preferably from 0.1 to 40, % by weight, based on (c1), of amino carboxylic acid B1, and
(c3) 0-5, preferably from 0 to 4, mol %, based on component (a1) from the preparation of P1 , of compound D.
The reaction of the polyesteramides P1 with amino carboxylic acid B1, if required in the presence of compound D, preferably takes place in the melt at from 120 to 260xc2x0 C. under an inert gas atmosphere, if desired also under reduced pressure. The procedure can be both batchwise and continuous, for example in stirred vessels or (reaction) extruders.
The reaction rate can, if required, be increased by adding conventional transesterification catalysts (see those described hereinbefore for the preparation of the polyesteramides P1).
When components B1 with higher molecular weights, for example with a p above 10 (ten) are used, it is possible to obtain, by reaction with the polyesteramides P1 in stirred vessels or extruders, the desired block structures by the choice of the reaction conditions such as temperature, holdup time and addition of transesterification catalysts such as the abovementioned. Thus, J. of Appl. Polym. Sci., 32 (1986) 6191-6207 and Makromol. Chemie, 136 (1970) 311-313 disclose that in the reaction in the melt it is possible to obtain from a blend by transesterification reactions initially block copolymers and then random copolymers.
The biodegradable polyesteramides Q2 according to the invention have a molecular weight (Mn) in the range from 5000 to 50,000, preferably from 6000 to 50,000, particularly preferably from 8000 to 35,000, g/mol, a viscosity number in the range from 30 to 450, preferably from 50 to 400, g/ml (measured in o-dichlorobenzene/phenol (50/50% by weight) at a concentration of 0.5% by weight of polyesteramide Q2 at 25xc2x0 C.) and a melting point in the range from 50 to 220xc2x0 C., preferably from 60 to 220xc2x0 C.
The polyesteramides Q2 are obtained according to the invention by reacting a mixture consisting essentially of
(d1) from 95 to 99.9, preferably from 96 to 99.8, particularly preferably from 97 to 99.65, % by weight of polyesteramide P1,
(d2) from 0.1 to 5, preferably 0.2-4, particularly preferably from 0.35 to 3%, by weight of a diisocyanate C1 and
(d3) from 0 to 5, preferably from 0 to 4, mol %, based on component (a1) from the preparation of P1, of compound D.
It is possible according to observations to date to employ as diisocyanate C1 all conventional and commercially obtainable diisocyanates. A diisocyanate which is selected from the group consisting of tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, 4,4xe2x80x2- and 2,4xe2x80x2-diphenylmethane diisocyanate, naphthylene 1,5-diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and methylenebis (4-isocyanatocyclohexane), particularly preferably hexamethylene diisocyanate, is preferably employed.
It is also possible in principle to employ trifunctional isocyanate compounds which may contain isocyanurate and/or biuret groups with a functionality of not less than three, or to replace the diisocyanate compounds C1 partially by tri- or polyisocyanates. The polyesteramides P1 are reacted with the diisocyanate C1 preferably in the melt, it being necessary to take care that, if possible, no side reactions which may lead to crosslinking or gel formation occur. In a particular embodiment, the reaction is normally carried out at from 130 to 240, preferably from 140 to 220xc2x0 C., with the addition of the diisocyanate advantageously taking place in a plurality of portions or continuously.
If required it is also possible to carry out the reaction of the polyesteramide P1 with the diisocyanate C1 in the presence of conventional inert solvents such as toluene, methyl ethyl ketone or dimethylformamide (DMF) or mixtures thereof, in which case the reaction is as a rule carried out at from 80 to 200, preferably from 90 to 150xc2x0 C.
The reaction with the diisocyanate C1 can be carried out batchwise or continuously, for example in stirred vessels, reaction extruders or through mixing heads.
It is also possible to employ in the reaction of the polyesteramides P1 with the diisocyanates C1 conventional catalysts which are disclosed in the prior art (for example those described in EP-A 534 295) or which can be or have been used in the preparation of the polyesteramides P1 and Q1 and, if the polyesteramides P1 have not been isolated in the preparation of polyesteramide Q2, can now be used further.
Examples which may be mentioned are: tertiary amines such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,Nxe2x80x2-dimethylpiperazine, diazabicyclo[2.2.2]octane and the like and, in particular, organic metal compounds such as titanium compounds, iron compounds, tin compounds, eg. dibutoxydiacetoacetoxytitanium, tetrabutyl orthotitanate, tin diacetate, dioctoate, dilaurate or the dialkyltin salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate or the like, it again being necessary to take care that, if possible, no toxic compounds ought to be employed.
Although the theoretical optimum for the reaction of P1 with diisocyanates C1 is a 1:1 molar ratio of isocyanate functionality to P1 end group (polyesteramides P1 with mainly hydroxyl end groups are preferred), the reaction can also be carried out without technical problems at molar ratios of from 1:3 to 1.5:1. With molar ratios of  greater than 1:1 it is possible if desired to add, during the reaction or else after the reaction, a chain extender selected from the components (a2), preferably a C2-C6-diol.
The biodegradable polymers T1 according to the invention have a molecular weight (Mn) in the range from 6000 to 50,000, preferably from 8000 to 40,000, particularly preferably from 8000 to 35,000, g/mol, a viscosity number in the range from 30 to 450, preferably from 50 to 400, g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polymer T1 at 25xc2x0 C.) and a melting point in the range from 50 to 255, preferably from 60 to 255xc2x0 C.
The biodegradable polymers T1 are obtained according to the invention by reacting a polyesteramide Q1 as claimed in claim 3 with
(e1) 0.1-5, preferably from 0.2 to 4, particularly preferably from 0.3 to 2.5%, by weight, based on the polyesteramide Q1, of diisocyanate C1 and with
(e2) 0-5, preferably from 0 to 4, mol %, based on component (a1) from the preparation of polyesteramide Q1 via polyesteramide P1, of compound D.
This normally results in a chain extension, with the resulting polymer chains preferably having a block structure.
As a rule, the reaction takes place in a similar way to the preparation of the polyesteramides Q2.
The biodegradable polymers T2 according to the invention have a molecular weight (Mn) in the range from 6000 to 50,000, preferably from 8000 to 40,000, particularly preferably from 8000 to 35,000, g/mol, a viscosity number in the range from 30 to 450, preferably from 50 to 400, g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polymer T2 at 25xc2x0 C.) and a melting point in the range from 50 to 255, preferably from 60 to 255xc2x0 C.
The biodegradable polymers T2 are obtained according to the invention by reacting the polyesteramide Q2 with
(f1) 0.01-50, preferably from 0.1 to 40%, by weight, based on the polyesteramide Q2, of amino carboxylic acid B1 and with
(f2) 0-5, preferably from 0 to 4, mol %, based on component (a1) from the preparation of polyesteramide Q2 via polyester-amide P1, of compound D,
the procedure expediently being similar to the reaction of polyesteramide P1 with amino carboxylic acid B1 to give polyesteramide Q1.
The biodegradable polymers T3 according to the invention have a molecular weight (Mn) in the range from 6000 to 50,000, preferably from 8000 to 40,000, particularly preferably from 8000 to 35,000, g/mol, a viscosity number in the range from 30 to 450, preferably from 50 to 400, g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polymer T3 at 25xc2x0 C.) and a melting point in the range from 50 to 255, preferably from 60 to 255xc2x0 C.
The biodegradable polymers T3 are obtained according to the invention by reacting (g1) polyesteramide P2, or (g2) a mixture consisting essentially of polyesteramide P1 and 0.01-50, preferably from 0.1 to 40%, by weight, based on the polyesteramide P1, of amino carboxylic acid B1, or (g3) a mixture consisting essentially of polyesteramides P1 which differ from one another in composition, with 0.1-5, preferably from 0.2 to 4, particularly preferably from 0.3 to 2.5%, by weight, based on the amount of the polyesteramides used, of diisocyanate C1 and with 0-5, preferably from 0 to 4, mol %, based on the particular molar amounts of component (a1) used to prepare the polyesteramides (g1) to (g3) used, of compound D, expediently carrying out the reactions in a similar way to the preparation of the polyesteramides Q2 from the polyesteramides P1 and the diisocyanates C1.
In a preferred embodiment, polyesteramides P2 whose repeating units are randomly distributed in the molecule are employed.
However, it is also possible to employ polyesteramides P2 whose polymer chains have block structures. Polyesteramides P2 of this type can generally be obtained by appropriate choice, in particular of the molecular weight, of the amino carboxylic acid B1. Thus, according to observations to date there is generally only incomplete transesterification or transamidation when a high molecular weight amino carboxylic acid B1 is used, in particular with a p above 10, for example even in the presence of the inactivators described above (see J. of Appl. Polym. Sci. 32 (1986) 6191-6207 and Makromol. Chemie 136 (1970) 311-313).
If required, the reaction can also be carried out in solution using the solvents mentioned for the preparation of the polymers T1 from the polyesteramides Q1 and the diisocyanates C1.
The biodegradable thermoplastic molding compositions T4 are obtained according to the invention by mixing in a conventional way, preferably with the addition of conventional additives such as stabilizers, processing aids, fillers etc. (see J. of Appl. Polym. Sci. 32 (1986) 6191-6207; WO 92/0441; EP 515,203; Kunststoff-Handbuch, Vol. 3/1, Carl Hanser Verlag Munich, 1992,pages 24-28)
(h1) 99.5-0.5% by weight of a polymer selected from the group of P1, P2, Q2 and T3 with
(h2) 0.5-99.5% by weight of a hydroxy carboxylic acid H1 of the general formula IVa or IVb 
where x is an integer from 1 to 1500, preferably from 1 to 1000, and y is 1, 2, 3 or 4, preferably 1 and 2, and M is a radical selected from the group consisting of phenylene, xe2x80x94(CH2)zxe2x80x94, where z is an integer from 1, 2, 3, 4 or 5, preferably 1 and 5, xe2x80x94C(R2)Hxe2x80x94 and xe2x80x94C(R2)HCH2, where R2 is methyl or ethyl.
The hydroxy carboxylic acid H1 employed in a preferred embodiment is: glycolic acid, D-, L- or D,L-lactic acid, 6-hydroxyhexanoic acid, the cyclic derivatives thereof such as glycolide (1,4-dioxane-2,5-dione), D-, L-dilactide (3,6-dimethyl-1,4-dioxane-2,5-dione), p-hydroxybenzoic acid and the oligomers and polymers thereof, such as 3-polyhydroxybutyric acid, polyhydroxyvaleric acid, polylactide (obtainable as EcoPLA(copyright) (from Cargill) for example) and a mixture of 3-polyhydroxybutyric acid and poly-hydroxyvaleric acid (the latter is obtainable from Zeneca under the name Biopol(copyright)).
In a preferred embodiment, high molecular weight hydroxy carboxylic acids H1 such as polycaprolactone or polylactide or polyglycolide with a molecular weight (Mn) in the range from 10,000 to 150,000, preferably from 10,000 to 100,000, g/mol are employed.
WO 92/0441 and EP-A 515,203 disclose that high molecular weight polylactide without added plasticizers is too brittle for most applications. It is possible in a preferred embodiment to prepare a blend starting from 0.5-20, preferably from 0.5 to 10%, by weight of polyesteramide P1 as claimed in claim 1 or polyesteramide Q2 as claimed in claim 4 and 99.5-80, preferably from 99.5 to 90%, by weight of polylactide, which displays a distinct improvement in the mechanical properties, for example an increase in the impact strength, compared with pure polylactide.
Another preferred embodiment relates to a blend obtainable by mixing from 99.5 to 40, preferably from 99.5 to 60%, by weight of polyesteramide P1 as claimed in claim 1 or polyesteramide Q2 as claimed in claim 4 and from 0.5 to 60, preferably from 0.5 to 40%, by weight of a high molecular weight hydroxy carboxylic acid H1, particularly preferably polylactide, polyglycolide, 3-polyhydroxybutyric acid and polycaprolactone. Blends of this type are completely biodegradable and, according to observations to date, have very good mechanical properties.
According to observations to date, the thermoplastic molding compositions T4 according to the invention are preferably obtained by observing short mixing times, for example when carrying out the mixing in an extruder. It is also possible to obtain molding compositions which have predominantly blend structures by choice of the mixing parameters, in particular the mixing time and, if required, the use of inactivators, ie. it is possible to control the mixing process so that transesterification reactions can also take place at least partly.
In another preferred embodiment it is possible to replace 0-50, preferably 0-30, mol % of the adipic acid or the ester-forming derivatives thereof or the mixtures thereof by at least one other aliphatic C4-C10- or cycloaliphatic C5-C10-dicarboxylic acid or dimer fatty acid such as succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid or sebacic acid or an ester derivative such as the di-C1-C6-alkyl esters thereof or the anhydrides thereof such as succinic anhydride, or mixtures thereof, preferably succinic acid, succinic anhydride, sebacic acid, dimer fatty acid and di-C1-C6-alkyl esters such as dimethyl, diethyl, di-n-propyl, diisobutyl, di-n-pentyl, dineopentyl, di-n-hexyl esters thereof, especially dimethylsuccinic acid ester.
A particularly preferred embodiment relates to the use as component (a1) of the mixture, described in EP-A 7445, of succinic acid, adipic acid and glutaric acid and the Cl-C6-alkyl esters thereof, especially the dimethyl esters.
In another preferred embodiment it is possible to replace 0-50, preferably 0-40, mol % of the terephthalic acid or the ester-forming derivatives thereof, or the mixtures thereof, by at least one other aromatic dicarboxylic acid such as isophthalic acid, phthalic acid or 2,6-naphthalenedicarboxylic acid, preferably isophthalic acid, or an ester derivative such as a di-C1-C6-alkyl ester, in particular the dimethyl ester, or mixtures thereof.
It should be noted in general that the various polymers according to the invention can be worked up in a conventional way by isolating the polymers or, in particular, if it is wished to react the polyesteramides P1, P2, Q1 and Q2 further, by not isolating the polymers but immediately processing them further. The polymers according to the invention can be applied to coating substrates by rolling, spreading, spraying or pouring. Preferred coating substrates are those which are compostable or rot such as moldings of paper, cellulose or starch.
The polymers according to the invention can also be used to produce moldings which are compostable. Moldings which may be mentioned by way of example are: disposable articles such as crockery, cutlery, refuse sacks, sheets for agriculture to advance harvesting, packaging sheets and vessels for growing plants.
It is furthermore possible to spin the polymers according to the invention into threads in a conventional way. The threads can, if required, be stretched, stretch-twisted, stretch-wound, stretch-warped, stretch-sized and stretch-texturized by customary methods. The stretching to flat yarn can moreover take place in the same working step (fully drawn yarn or fully oriented yarn) or in a separate step. The stretch warping, stretch sizing and stretch texturizing are generally carried out in a working step separate from the spinning. The threads can be further processed to fibers in a conventional way. Sheet-like structures can then be obtained from the fibers by weaving or knitting.
The moldings, coating compositions and threads etc. described above can, if required, also contain fillers which can be incorporated during the polymerization process at any stage or subsequently, for example in a melt of the polymers according to the invention.
It is possible to add from 0 to 80% by weight of fillers, based on the polymers according to the invention. Examples of suitable fillers are carbon black, starch, lignin powder, cellulose fibers, natural fibers such as sisal and hemp, iron oxides, clay minerals, ores, calcium carbonate, calcium sulfate, barium sulfate and titanium dioxide. The fillers can in some cases also contain stabilizers such as tocopherol (vitamin E), organic phosphorus compounds, mono-, di- and polyphenols, hydroquinones, diarylamines, thioethers, UV stabilizers, nucleating agents such as talc, and lubricants and mold release agents based on hydrocarbons, fatty alcohols, higher carboxylic acids, metal salts of higher carboxylic acids such as calcium and zing stearate, and montan waxes. Such stabilizers etc. are described in detail in Kunststoff-Handbuch, Vol. 3/1, Carl Hanser Verlag, Munich, 1992, pages 24-28.
The polymers according to the invention can additionally be colored in any desired way by adding organic or inorganic dyes. The dyes can also in the widest sense be regarded as filler.
A particular application of the polymers according to the invention relates to the use as compostable sheet of a compostable coating as outer layer of diapers. The outer layer of the diapers effectively prevents penetration by liquids which are absorbed inside the diaper by the fluff and superabsorbers, preferably by biodegradable superabsorbers, for example based on crosslinked polyacrylic acid or crosslinked polyacrylamide. It is possible to use a web of a cellulose material as inner layer of the diaper. The outer layer of the described diapers is biodegradable and thus compostable. It disintegrates on composting so that the entire diaper rots, whereas diapers provided with an outer layer of, for example, polyethylene cannot be composted without previous reduction in size or elaborate removal of the polyethylene sheet.
Another preferred use of the polymers and molding compositions according to the invention relates to the production of adhesives in a conventional way (see, for example, Encycl. of Polym. Sc. and Eng. Vol.1, xe2x80x9cAdhesive Compositionsxe2x80x9d, pages 547-577). The polymers and molding compositions according to the invention can also be processed as disclosed in EP-A 21042 using suitable tackifying thermoplastic resins, preferably natural resins, by the methods described therein. The polymers and molding compositions according to the invention can also be further processed as disclosed in DE-A 4 234 305 to solvent-free adhesive systems such as hot melt sheets.
Another preferred application relates to the production of completely degradable blends with starch mixtures (preferably with thermoplastic starch as described in WO 90/05161) in a similar process to that described in DE-A 42 37 535. The polymers according to the invention can in this case be mixed both as granules and as polymer melts with starch mixtures, and admixing as polymer melt is preferred because this allows one process step (granulation) to be saved (direct finishing). The polymers and thermoplastic molding compositions according to the invention can, according to observations to date, because of their hydrophobic nature, their mechanical properties, their complete biodegradability, their good compatibility with thermoplastic starch and not least because of their favorable raw material basis, advantageously be employed as synthetic blend component.
Further applications relate, for example, to the use of the polymers according to the invention in agricultural mulch, packaging material for seeds and nutrients, substrate in adhesive sheets, baby pants, pouches, bed sheets, bottles, boxes, dust bags, labels, cushion coverings, protective clothing, hygiene articles, handkerchiefs, toys and wipes.
Another use of the polymers and molding compositions according to the invention relates to the production of foams, generally by conventional methods (see EP-A 372 846; Handbook of Polymeric foams and Foam Technology, Hanser Publisher, Munich, 1991, pages 375-408). This normally entails the polymer or molding composition according to the invention being initially melted, if required with the addition of up to 5% by weight of compound D, preferably pyromellitic dianhydride and trimellitic anhydride, then a blowing agent being added and the resulting mixture being exposed to reduced pressure by extrusion, resulting in foaming.
The advantages of the polymers according to the invention over known biodegradable polymers are a favorable raw material basis with readily available starting materials such as adipic acid, terephthalic acid and conventional diols, interesting mechanical properties due to the combination of xe2x80x9chardxe2x80x9d (owing to the aromatic dicarboxylic acids such as terephthalic acid) and xe2x80x9csoftxe2x80x9d (owing to the aliphatic dicarboxylic acids such as adipic acid) segments in the polymer chain and the variation in uses due to simple modifications, a satisfactory degradation by microorganisms, especially in compost and soil, and a certain resistance to microorganisms in aqueous systems at room temperature, which is particularly advantageous for many applications. The random incorporation of the aromatic dicarboxylic acids of components (a1) in various polymers makes the biological attack possible and thus achieves the desired biodegradability. A particular advantage of the polymers according to the invention is that it is possible by tailoring the formulations to optimize both the biodegradation and the mechanical properties for the particular application.
It is furthermore possible depending on the preparation process advantageously to obtain polymers with predominantly random distribution of monomer units, polymers with predominantly block structures and polymers with predominantly blend structure or blends.